Prefabricated structure for containers and the like



1 r H. B. LINDSAY 2,364,083

BREFABRICATED STRUCTURE FORCONTAINERS AND THE LIKE Filed June 7, 1943 2 Sheets-Sheet l 32 INVENTOR- GW a/Qv Dec. 5, 1944. 2,364,083

PREFABRICATED STRUCTURE FOR CONTAINERS AND THE LIKE H. LINDSAY Filed June 7, 1.943 2 Sheets-Sheet 2 INVENTOR.

Patented Dec. 5, 1944 UNITED STATE.

s PATIENT OFFICE mm mm smuc'rrma Fox 'nai-v yn. mum, Evanston, m, assignor to liflndsay dz Lindsay, Chicago, 11]., a partner- Application Jone 7.194s, Serial N... masts u Claimsw(cl. 189-44) This invention relates to improvements in Dre fabricated structures of relatively light wei h made ,of metal or othermaterials, adapted for containers, boxes, partitions, housings, furniture. and similar strueturea consistin'g primarily of.

polygcnally disposed frame members y relativelythin sheet panelmembers.

Among the objects of the invention is panel members, all -of' simpleioi which can to provide a structure consisting of frame 'members and be made up in predetermined shapes and sizes for structures 'of various kinda and shipped in knockdown condition, whosecost will be -re1a-' tively low, and which on assembly will provide structures of sufllcient strength and-rigidity for the purposes above suggested: I s I A further object is-toprovide structure of the character described, which be assembled without the'use of any bolts,-screws, nails, rivets, or welding means. Instead, the

, a'san intermediate support ,between two panels in'th'e ame plane; I Figure 7 is a'transverse detail view similar to Figure 2, but showingan additional flange-lockling arrangement'fcr the panel members, which .is capable of being more positiveiylocked or unlocked by means of a tool, when desired: Figure 8 is a perspectivevlew of a corner fastening structure especially adapted for connecting the meeting ends of frame members atcornerofarectangular structure;

v Figure 9 is aperspective view showing max; panded relation'tiie arrangement .of the three component parts of the structure shown in Figlire 8; v

Figure 10 is a planview of a blank sheet metal fastening member from which'is-formed each of the three component parts of the fastening structure shown in Figures 8 and 9; Figure 11 is a perspective view illustrating the sheets are attachedto the framing by means of. a novel interlocking configuration of sheets'and framing, whereby the sheets are gripped or locked in.place and become firmiysecured to the framing, so as to tie the entire structure together.

The locking means is such that the rigidity and gripping effect is increased by the application of normal stresses on the structure.

Other objects and advantages will appear from time to time as the following description proceeds i.

The invention may best be understood by reference to the accompanying drawings, in which- Figure -l is a per pective view showing an-enclosed container made in accordance with my in vention;

Figure 2 is an enlarged detail section takenonline 2--2 of Figure 1, but with the exterior corner trim removed, to illustrate the essential or basic structural elements, consisting of a frame memher and panels, and showing the method'of assembly or connection of the panels thereto;

Figure 3 is aperspective view showing frag-' mentary portions ofv the frame and- 'panels before assembly;

Figure 44 is a transverse sectional "view-. drawn on a somewhat smaller scale than Figure 2, showing amodifled form of frame member-and corresponding p nel structure; Figure 5 is a sectional .view of the frame and panelstructure of the type shown in Figure 4,

method vof assembly of the frame members and the three component parts of the corner fastening structure shown in Figure 8-, by inserting the projecting, arms of said corner fastening structure into the ends of the frame members;

Figure'l2 is an enlarged detail section taken on line i2--i2 of Figure l to show a portion of the corner fastening assemb y. after it is inserted within the adjacent end of onset the frame members;

Figure 13 is a persi lective'view of the corner assembly, but showing an outer corner cap memher which is applied thereto;

Figure 14 is a tr verse section showing the '35 arrangement of a container-provided with bothvv inner and outer walls, constructed in accordance withmy invention; 7 v "Figure 15 is a detail perspective view of the comer cross-brace membershown in Fig re 14;

Figure 16 is a transverse detail section showing but with a snap-on edge trim member also applied to the framework e is a sectional view showing a modified form of frame member which may be employed a novel form of support or 'hanger which may be employed with the outer corner frame members of my structure, so as, to provide a support for a shell or other portion members within thestructure;-and r i I side view of the supp rt or hanger Figure g'is a 16 shown in gure i I w Referring now to details of the embodiment of my invention in the drawin s. yp cal rectangular-container constructed-in accordance. therewith is indicated at. II in Figure 1. The principal elements which go to make up the structureareshcwnindetailinl 'igurea2and3 and consist-of a plurality of frame members indictated generally at'fll and panel in-' dicatedgenerally at l2. The frame members 'are'suitably connected together at theirends, as

will-hereinafter 'be described in detail, to form an open framework of generally rectangular shape. The panel members |2, |2, forming the outer walls of the structure, are provided with flanged mar-- gins having interlocking engagement with the frame members. I I

The means affording interlocking "engagement between the margins of the panels l2 and each" proximate frame member II is provided in the following manner, as illustrated in Figures 2 and 3: Theframe member consists essentiallyin alength of relatively stiff material, such as sheet metal, which is formed by bending the strip longitudinally upon itself so as to provide a centrally disposed C-shaped head I5. a'pair of laterally spaced parallel webs l8, l6, extending in-: wardly from the opposed .inner ends ..of.- the c-shaped head l5, and a pair of reversely bent,

outwardly extending webs l1, l1, disposed at" equal angles from the, inner ends of their respective webs l6, l6. The-webs lt and ll'thus form and one-half times the thickness of said flange.

.Thecornerformed by the junction of the outside faces of'the web It and the shoulder I511 (or a tangent thereto), is preferably an angle of not more than 90 degrees, as shown in Figure 2. Figure 4 shows a modification in which a very shallow groove 22a is formed in the surface of the shoulder contiguous to said corner, such .groove having a width very slightly wider than the thickness of the edge'of flange 22.

It will be especially noted .that when the acuteangled flanges of. the panel l2 are locked in the frame member, they are securely held against accidental displacement therefrom. Any forces which ordinarily may be exerted on the panel |2 will tend to'increase the gripping action of the a pair of outwardly open V-Qshaped grooves' l8, l8 inthe frame member, alongopposite .sides of the head I5. The two outer-webs ll, I are disposed substantially atright angles to locking flanges in the groove l8. rather than release them. "For instancaany stresses on the in the wedging action of the v-shaped .flanges eachothen-and their connecting webs l6 are arranged at an angle of about .45 degrees thereto. In the form of frame member shown in Fig ures jacent weh' l6. and thatthe ffee vendsxii-the outer webs terminate slightly beyond the head l5 when measuredin lines projected Perpendicularly of said outer webs ll. H. The free ends and 3; it will be noted that the outerends of the webs I l are somewhat longer than the adof eachof the webs I1, are curved outwardly I to form a relatively short flange |9. Each of th panels-|' 2. |2 consists of a flat body portion 20 or sheet metal; which is surrounded by an inner flange 2| and an outer, flange 22 arranged at a.reverse acute angle to the flange .2l. The inner flange 2| is disposed at an angle or approximately 90 degrees to the body; 20 and the outer flange22 is normally disposed at an angle of slightly more than-45 de-- grees from the flange 2|. The two flanges 2| and 22 are preferably formed by press drawing the margins of the sheet metal panel in the usual manner between male and female dies of the proper shapes.

The arrangement is such that-the acute-angled flanges 2|and 22 will flt snuglyin an adjacent V-shaped groove l8 of thi frame member 'The-outer flange 22 is of such-length asto engage the inner web It of said frame member,

1 with its-outer or free end fltting'beneathand engaging the overhanging shoulder I informed by the C-shapedhead IS, as shown inFigur'e 2. As previously stated, the outer flange 22 of panel 20 is disposed normally at an angle slightly greaterthan 45 degrees to the flange 2|. The arrangement is' such thatwhen the flanges 2| and 22 or the panel are inserted in the V-sha'ped groove 18 under moderate pressure, the flange in said frame.

It is also to be noted that (particularly in the case of very thin metal or othervless stiff sheet material), the junctionbetween flanges 2| and- 22 should. be a sharp bendrather. than a curve ofv larger radiusralso z that flanges 2| and 22 should be flat,: not curved: these for the reason that under severe tension metal (and other materials) will -,follow"yand so pull out round a curve, but cannot do this and will remain flxed and rigid at apoint' of sharp acute bend.

Figure 4 shows a modified form of frame mem- 4 her wherein the free ends of the outer webs H, II terminate in squared extremities, instead of outwardly curved ends or flanges It, as shown in Figures 2 and 3. I flnd in practice that the provision of the curved ends I9, I 9 of Figure 2 has certain advantages, since it presents a curved, rather than a relatively sharp, cutting edge to the panel. Also the flange 2| joins the panel 20 with acurved, rather than a sharp corner, which may havea tendency to weaken the panel structure, and this curved comer serves to increase the pressure of flange 22 against web It (and consequently the pressure ofthe free edge of flange 22 into the comer oiweb l6 and shoulder I5a), upon tensional stresses being set up .in sheet body 20 tending to pull the sheet from the framing. Moreover, the curved end IQ of Figure 2 permits a limited'variation in the relative depthsof the locking flange 2| and the groove 8, in case minor inaccuracies may occur "in the initial formation of theseinterlocking 22 will snap into place immediately and become looked under tension beneath the shoulder I51:

and 4.

Toeause this eflect of flange 22 snapping into place without permanently deforming angle 1 between flanges 2| and 22, the overhang of shoulder Iia (measured on a line parallel to web l6) is preferably not greater than flfteen per cent of the length or flange 22, nor less than one of frame member II, as indicated in Figures 2 parts. t I

.Figure 5' shows a corner frame structure, including a-flnishing strip or flller 25,.which may be formed of a length of sheet metal having its 1 ends 26 bent rearwardly in S-like shape so as to be detachablv eng ed neath the opposite sides of the head |5.- When assembled in this manner, the finishing strip presents a curved edge surfacesubstantially flush with the panels l2, l2 and fllling the space at opposite sides of the head lj such an edge finishing strip 25 is provided mainly for enhancing the appearance or attractiveness-of the structure.

Figure 6 shows a. modified form of frame member, indicated at Ila, which is particular'lyldesigned for use as an intermediate'cross brace toaseaoaa of the' corner frame member l, respectively, err--- cepting that the webs I60, |6a are spread apart at an angle of approximately 90 degrees to each other, instead of being parallel to each other, as in the case of the corner-frame members- Actually thisframe member is preferably frame member press-spread from center 90 degrees Figure 7 illustrates a modifled form of panel fastening, having locking meanaconsisting of a terminal flange 28 formed at the end of the outer flange 22 of the panel l2. The terminal flange 28 is initially formed substantially at. a right angle to the outer flange 22, as shown in the upper part of Figure '7. After the flanges. 2| and 22 have become seated in the V-shaped groove |8, however, the terminal flange 28 may be depressed by means of a suitable tool. indicated in dotted:

flanges 33, 83 is engaged with the adjacent inner ends of the webs l8, so as to hold the three frame members connected to each corner fastening device against lateral displacement relative to said fastening device. and to each other.

The method of assembly of a structure consisting of the elements hereinabove may now be described as follows: The framework is first assembled by applying the ends of theframe members cut to proper lengths, to the assembly 1 When the framework is completed, the panels lines in thesame figure, so that the squared free edge of the locking flange 28 will become engaged with the opposed surface of the flange 2| at right angles to the latter, as clearly shown in this fi ure.

The flange 2a is made of such length that its can be readily released by using asuitable tool,

either by forcing th flange 28 inwardly, or-by prying the edge of'said flange outwardly from its upright locking position.

The locking flange 28 i advantageousln Y ,wherea tightly sealed joint 'is desired, and also in cases where the structure is to be dismantled or disassembled from time to time, without injury to the interlocking flanges of th panels. It is especially .useful in cases where its panelis to 'be employed as a removable closure for the container.

Refening' now more particularlyto the means 'for connecting the meeting ends of the frame members II at the corners of the container It], a preferred form of fastening device 30 is shown in Figures 8 to 11. andis made up of three said angle pieces is made from a blank of sheet metal c'ut in'the form shown in Figure 10, wherein two similar wings 32, 32 are initially formed at an angle of'-120 degrees to each other. The two wings 32, 32 of each angle piec are bent at an angle to each other, and inner and outer marginal flanges 33. 33 and 34, 34 are also bent inwardly along their outer sides, as clearly shown in Figure 9.

Three similar angle pieces 3|, all formed in the same manner, are nested together, in back-toback relation, as indicated in partially assembled nandtie the entire structure -together.

20 20 are applied to the open framework by snappin the locking 2|, 22, in the proper position relative to the groovesl8 formed along the frame members. J I a When the panels, 2|! are 'thus applied to the structure it will-be understood thatthey will hold the frame members H from endwise withdrawal from the corner fastening devices 30, 30,

k 1 Accordingly, the several parts co-operate to form a unitary stucture which will. be' maintained in'assembled form without the of extraneous fastening devices,-such as bolts, screws, or the like.-

A structure made infaccordance with 'my in-.

vention exhibits great strength and resistance,

particularlyin view of the lightness'of the parts which maybe employed-,imthe. construction of the frame members I andparticulai'ly 'the pan els l2. llltwlll he.IIIldEst (2)011 ""that; the-frame -members "(are preferably-formed of heavier gauge'metal, or stifler material, than thepanels $512, so as to provide the jdesired,. j'streiigth of the t entirestructure, as-well .flsto resist distortion of the locldngagro'oves-fw Finally, the edge"trim members 25, 25 may be applied to theunitaryfstructure', as-previolisly described in lcounectionwithFi e 5.

- Rigiditymand lack 'o'ff'give or "working" are essential in the purposes 10 this invention and consequently the 'supportfgiven .the lighter sheet by the stouter frame over theentire fastenin area, prevents, anygive'orcollaps'e of the former inthisvitalarea. Q

It is important to;

of the frame grooves l8, the importance of the flanges (particularly flange 22) and groove walls (particularly of web I6) I being flat, is at once apparent. In ,this case the outward tension exerted on the flange 2| immediately causes a compressing or wedging action of flange 22 between the inner face of web H (near the bottom of the V) and the flange-e'dge-abutment against shoulder I511. The flange 22, being. itself plane in the planeo'f compression: will stand tremendous compression *stress for. its thickness with- ,position in Figure sand in fully assembled posipair of Wings 32. 32 in the slot, formed between 7 the opposed webs IS, H5 at the end of one of said A frame members. As will be seen in'Figure 12. the outermostfpair of flanges 34, 34 is adapted to fit snugly within the C-shaped head out bending or "collapse, "Hence, this prevents any loosening of the sheet and consequent working and collapse of'the structure.

If, on the other hand. flange 22 be curvedrr bent it would stand relatively speakingvno compression force. and in addition the thin she t metal or similar material would readily "follow"- any severe tension by drawing round the curve andout. i

It should also be noted that the relat vely l ht sheet material 2 in myinvention in coniu ction with the above," is positively s pport against Jeosening under. stress. by th vouter ed e of the welrtl of the relatively stout-frame memthe frame member, and thelowermost pair of "hen Any give of the sheet at this point would it :'.under excessive I note that I under stresses similar sheet metal angle pieces 3|, 3|. Each of tending to drag the sheet/flanges 2| and 22 out 4 t likewise result in working and eventual collapse ofthestructure.

- Figure 13 shows in detail a form of comer cap member 24 which may be employed to e'over the exterior of eachcorner of the structure after the latter has been assembled; In the form' shown, said corner member consists ofa partially spherical piece of sheet metal 21 which is formed to fltover and enclose the space between the meeting comersof thepanels 20,20 at each I corner of the structure. Said corner trim mem-- ber has a plurality of yielding inwardly extend- The two intermediate frame members Ha, He may be spaced by somewhat similar bars or straps 35a. 85a, having their diverging outer ends engaged in the heads |5b of said frame members, in substantially the same manner as heretofore; described in connection with the inner corner frame member ||b.

Figures 16 and 17 illustrate how the outer comer members may also be utilized for detachably mounting a Suitable support for partiytion members or trays which may be employed ing'flngers 29, 29 attached on its under face,

adapted to be snapped into engagement on opposite sides 'of the outer flanges 34, "34 ofthe adjacent corner fastening "members 30, 30, .afterthe frame members II have been attached to the latter, and the panels 20, 20 have been applied to the structure. The corner trim memhas 24 and edge trim'memb'ers 25 thus provide a finished appearanceltothe structure, and help 1 to protect the edges and comers 1 tmfm.

fture from injury. Thewcompositestructurelis able to withstand exterior and interior stresses t .,an'astonishingdegree,in' the manyj-uses-to similarestructure. ofthisf which a container or character maybe employed.' -'-It also be understoodth ta double walled container may be made in accordance {with the,

structural principles heretofore and- 7 shown, as illustrated in 14'and 15., r

In Figure 14 the outer'wall is m ce -s ub'stan tially as hereinbefore described, including corner-x; frame members intermediate-flame members.

Ila, and outer panel members 12,712; 'Iheinner wall is constructed with cross frame members ||b,' which are'substantially of the sameeross- 1 within the container; As shown in Figure 16,

such a support is indicated at 40 and consists of apiece of sheet metal which is bent upon itself and provided with a pair of flanges 4|, 4|, extending outwardly from each other at one end thereof, so as to flt between the webs l6, l6 ,of

=th frame member II, with the end flanges 4|.

engaged within theft-shaped head I5.

Said support is also provided within depend-; fling portion 42 having laterally extending flanges 43, connected therewith. These flanges are adapted to engage the adjacent inner faces oi the frame member H as shown in Figure 17, so

.-indic'ated ,at 44, extending and normally hold the support at any desired as-to resist vertical stresses upon the support point. The support 40 may therefore be slidably, adjusted along the frame member l to any desired level. Said support may also be anchored at any desired point, as by a set-screw through the outer face of the c-shaped-head l5 into engagement -with'the proximate faces of the flanges 4|, 4| of said support:

The support 40 may also be made in different shapes, as, for instance, indicated in dotted lines at 45, 45, wherein the projecting portion of said sectional shape as the Wrxiiediate' frame mefn bers |a. Where/another intermediateffraine" member is required, inthe inner wall,-;it 'may also be of the same form as the intermediate frame member He used on the outerwall, as"

clearly shown in Figure 14? The inner panels In, |2a willbe similar in 35, 35, which project in the slot betweenf'the webs 6, l5 of the outer frame member l.|. Said bars also have outwardly'flanged ends It, 35, which are adapted to fit iii-the C-shaped head l5 of said outer-frame member and outwardly flared inner ends 31, 31, which engage in the slots at. the opposite ends of the C-shaped head lid of the inner frame member llb, as clearly shown in Figure 14. Thetwo bars or straps 35, 35 are applied inback-to-back relation to the frame members ll, ||b, by slipping them into-the ends of said frame members. Aplusupport may be extended lateral gular. form if desired.

Although I have shown and, described a preferred embodiment of my invention, it is to be understood that I do not wish to be limited to the "exact embodiment of the device shown, which. is merely by way of illustration and not limitation, as various other forms of the device will, of course, be' apparent to those skilled in the art without 'departing from the spirit of the invention and scope of the claims.

I claim: e 1. A composite structure comprising panel sheets and frame members, the frame members having longitudinal grooves formed therealong of generally acute angular cross-section, each ofsaidgrooves on-the edge farthest from the intended position of the panel having an overhanging shoulder therealong and each of said 1 panel sheets being provided with two' acuteangled flanges formed along their margins, having wedge-fitting engagement in said groove,

with the free outer edge'of the outer flange I abutting said shoulder.

2; In a composite structure c'omiprising panel sheets and frame members, the combination of .panel sheets having two substantially flat marginal flanges arranged at an acute angle to each other and with the free edge of the outer flange disposed beyond its respective inner flange and -panel, and frame members having rality of such straps may be provided, if it is desired to hold said straps 'at predetermined p intselong the frame members; said Straps may be anchored, as by means of a ,set-screw 39, threaded'through the outer face of the c-shaped head lbofframemember ll.

5 said 'and' said. frame member.-- I

substantially correspondinglyshaped grooves formed'therein, with an overhanging shoulder having abutting engagement with the 'free edge of the outermost acute angled flanges of said panels and said flanges-fitting in said grooves, to provide an interlocking connection between ly into a trianfastening structure being plurality. of continuous grooves along opposite plurality ofwpanel sheet mem-' edges thereof, each of said grooves having outwardly flaring .side walls disposed at an acute angle to each other, and the side walls farthest Id of v-shaped grooves, said corner fastening strucfrom the adjacent edge of said frame member havingan overhanging shoulder along its outer edge, and said panels being formed with interlocking -flange means "engageable said grooves, each consisting'of two reversely bent marginal flanges disposed at an acute angle to each other and fitting in one of said grooves with'the free edge of the outermost flange re tained in locking engagement beneath the overhanging shoulder ofitsrespective groove.

4. In a compositestructure including frame 9,0

members and panel sheets,said frame members -being formed of strip metal bent longitudinally to form an enlarged centrally disposed head, two similar web portions extending inwardly from said head, and a web'portion bent out- 5 wardly from-the inner end of each of said first- .named webs to form apairof grooves of gener- Qally' acute angular cross-section, said head forming an overhanging shoulder along eachof said grooves and the margins of each of said anel sheets being provided with twoacute- 'f anglal flanges fltting into one of said grooves,

7. In a composite structure comprising panel sheets, frame members and corner fastenin structures, each of said frame members being formed of a metal strip bent longitudinally upon" itself to provide an enlarged head, a pair 'of laterally spaced inwardly extending webs connected to opposite sides of said head, and c terminal web bent outwardly from the inner end of each of said first-named webs to form a pair tures each comprising three similar angle pieces made of sheet metal andbent into shape so as to engage each other in back-to-back'relation to form a single fastening unit with three arms disposed at right angles to each other to define a corner of the structur the arms of said corner fastening structure being adapted to be inserted in fitting engagement in the adjacent ends of a s frame member in the spacesbetween the inwardly with the free edge .of the outer flange in abuttin engagement with the shoulder of said groove. 7 e

.5. In a composite structure including frame members-and panel sheets, said frame members being formed of strip metal bent longitudinally to form'an enlarged hollow centrally disposed .head, two similar web'portions extending in- .wardly from said head and spaced from each other, and a web portion bent outwardly from the inner end of each of said first-named webs to form a pair of grooves of generally acute angular' cross-section, said head forming an over- I shoulder along each of said grooves and said panel sheets having correspondingly shaped acute-angled flanged margins fitting in said grooves, to provide interlocking engagement between said flanges and grooves, and said spaced webs having fastening -members therebetween,'with flanged extremities extending into said head.

6. In a composite structure comprising panel sheets, frame members and corner fastening structures, each of said frame members being formed of a strip of metal bent longitudinally upon'itself'to .provide an enlarged head, a pair of laterally spaced inwardly extending webs connected to opposite sides of said head, and a ter- 60 web bent outwardly from the inner end minal of each of said first-named webs to form a pair of V-shaped grooves, said corner fastening structures each comprising three similar angle pieces made of sheet metal and bent into shape so as to engage each other in back-to-back relation to form a single fastening unit withjhree arms disposed at right angles to'each other to define a corner of the structure, the armsof said corner adapted to be inserted in fitting-engagement in the ends of adjacent frame members, and said panel sheets havin flanged marginal edges adapted to have interlocking engagement in the acute-angled grooves formed in said members.

40 overhanging shoulder 5 form cross-section adjacent sides extending webs thereof, and said panel sheets having flanged marginal edges adapted to have interlocking engagement in the acute-angled grooves formed in said frame members. a i

'8. A composite structure comprising panel sheets and frame members, the frame members having longitudinal grooves formed therealong, -each of said grooves having disposed at an acute angle to each other, and the side wall farthest from the intended position 30 of the adjacent panel sheet having an overhanging shoulder therealong, each of said panel a sheets having marginal interlocking nieans ineluding tworelatively yieldable locking flanges fitting in said grooves with said flanges in regis- 35 tering engagement, respectively, with the side walls of said grooves, and the free edge of thev outer flange being normally-disposed with relation to the inner flange so that saidfree edge engages under expanding tension beneath the of said groove; -9. A composite structure comprising pane sheets having elastically bending characteristics similar to thin sheet metal, and relatively stifler frame members, said frame members having unipresenting two acute-angled flat-sided grooves, their adjacent walls being spaced apart and joined together along their adjacent edges by 'an expanded portion forming a projecting shoulder into each groove on the, thereof, and said sheets having v-shaped flanges normally of less acute angularity than said grooves pressed into said grooves past said shoulders into snug flt therein with the free edges of said flanges in looking abutment against said shoulders.

I along of generally acute-angled cross-section and 5 its margin 7 sheet relative with a locking shoulder overhanging the edge of said groove farthest removed from the intended position of connection .of said panel sheet, said 4 panel sheet being relatively non-rigid and having two flat oppositely bent flanges formed along at acute angle to each other and having wedge-fitting engagement in the, groove in said frame member with the free edge .of the outermost flange engaged beneath said locking shoulder so that transverse stresses on said panel to said frame member will tend to increase the locking action of said outer flange beneatlf'safd locking shoulder. I 11. A "composite structure including a panel sheet and a frame member, the frame member having .a longitudinal groove therealong formed opposed side walls of opposed side walls disposed at an acute angle to each other, and the side wall farthest from the intended position of the adjacent .panei sheet having an overhanging shoulder therealong, said panel sheet having marginal self-looking means cooperating with said groove, including two flanges normally 0! less acute angularity than the walls of saidgrooves and wedge-fitting into said grooves past said shoulder with the free edge of the outer flange in abutting engagement beneath said shoulder so as to maintain the inner flange in looking engagement against the opposite wall of said groove.

HARVEY B. LINDSAY. 

